Scanning system for revolving creel type circular knitting machines



Oct. 10,1967 R. B. FERTIG ET AL 3,345,836

' SCANNING SYSTEM FOR REVOLVING CREEL TYPE CIRCULAR KNITTING MACHINES Filed Jan. 26, 1966 4 Sheets-Sheet l IHg-i H AD l4 J74 T/O/VA R Y J UGAJIEM Bi V PEGUL A r50 Pan 5e JUPPL Y (0 L L E C 7'0 2 IP VF PEIWO-EEIZECf/VE ,e/wo

INVENTOR 5 ATTORNEYS R. B. FERTIG ET AL 3,345,836 SCANNING SYSTEM FOR REVOLVING CREEL TYPE CIRCULAR Oct. 10,1967

KNITTING MACHINES.

4 Sheets-Sheet 2 Filed Jan. 26, 1966 all INVENTOR: karma/v0 dam/es #2? 776 [Aimee-Mrs @57 Maze-4 z.

ZA AQU gbhm ATTORNEYS mas Oct. 10,1967 [FET.G ET AL 3,345,836

SCANNING SYSTEM FOR REVOLVING CREEIL TYPE CIRCULAR KNITTING MACHINES v Filed Jan. 26, 1966 4 Sheets-Sheet 3 INVENTORS 4 A ter/a [aw/ears flea-w Ma e-44 ATTORNEYS TY) wane.

06L 10,1967 FERT|G ET AL 3,345,836

SCANN ING SYSTEM FOR REVOLVING CREEL TYPE CIRCULAR I KNITTING MACHINES I Filed Jan. 26, 1966 4 Sheets-Sheet 4 +l5o V M.

roceu.

ATTORNEYS Ziwea-wrs (ks/a Mme-44 BY 3 P W mung) wwu,

United States Patent ABSTRACT OF THE DISCLOSURE A fabric flaw detecting apparatus on a stationary needle cylinder circular knitting machine. A lamp and lens directed toward the fabric tube and a photocell are commonly housed and mounted on a rotating plate interior of the fabric tube along with amplification and regulated power supply circuitry. Additional circuitry exterior of the fabric tube is joined with the regulated power supply through a wiper member which contacts a ring above the machine dial rotatable with the plate interior of the fabric tube and wired to the regulated power supply. A stationary ring of retro-reflective material exterior of the fabric tube being knit returns any light passing out through a flaw in the tube back to the photocell which gives rise to a pulse which is amplified and sensed to operate a stop motion.

The present invention relates in general to fabric flaw detector systems for circular knitting machines, and more particularly to optical scanning apparatus and associated circuitry for scanning and detecting holes and aperture flaws, in tubular knit fabric as the same is knitted by circular knitting machines of the revolving creel type wherein the fabric does not rotate as it is discharged from the needles.

The desirability of promptly detecting holes, runs, or similar aperture flaws in knitted fabrics as the fabric 'leaves the zone of the needles of a knitting machine so that the machine can be immediately stopped to minimize production of defective fabric and reduce consequent wastage of materials and time has been long recognized. Such fabric scanning and flaw detecting systems have been commonly referred to in the trade as stop motion devices, and have been used for many years on tricot knitting machines of the type which produce flat fabric webs. In such cases, a photoelectric sensing head is scanned transversely across the fabric, which may either be back-illuminated or front-illuminated by a stationary light source, or may be illuminated by a light source which is scanned in coordinated relation with the detector head (usually by incorporating both the photocell and light source in the same detector head structure). Holes or similar flaws in the fabric produce a variation in light sensed by the photocell, producing an output signal which activates appropriate circuitry to produce an alarm indication and/or stop the knitting machine.

More recently, an embodiment of a stop motion system has been disclosed in a United States patent application filed by Lawrence Creigh Nickell and Raymond Baines Fertig, Ser. No. 417,697, filed Dec. 11, 1964, which includes a stationary scanning head having a photocell and light source therein mounted immediately below the fabric tube produced by a circular knitting machine of the stationary creel type to scan the fabric tube as it leaves the circular set of latch needles and activate an alarm and/ or stop the circular knitting machine upon detection of a hole or similar flaw. As the needle cylinder, sinkers, take-up rolls and thus the fabric tube in such machines all rotate about the vertical axis of rotation of the needle cylin- 3,345,836 Patented Oct. 10, 1367 hoe der in such machines, the stationary detector head scans a spiral path of small pitch around the fabric tube knit by the machine to effectively sense all parts of the fabric tube. A body or surface of retro-reflective material is located within the fabric tube leaving the needles in line with the optical axis of the detector head to redirect light from the light source in the detector head which passes through the fabric hole, when a hole is encountered, back to the photocell in the detector head and produce the hole-indicating signal. However, such a flaw detecting system cannot be used in circular knitting machines of the revolving creel type, wherein the needle cylinder does not rotate and thus the fabric tube leaving the needles does not rotate. Consequently, a stationary scanning head would sense only a narrow band along the axial length of the fabric tube at one radial position as the latter moves downwardly from the needles, thus scanning only along a vertical line paralleling the vertical center axis of the needle cylinder.

. To permit scanning of the entire circumference of the fabric tube in such a revolving creel type circular knitting machine it is therefore necessary to rotate the detector head, preferably within the fabric tube and about a vertical axis extending through the center of the needle cylinder, so as to scan a path extending entirely around the fabric tube. However, a rotating detector head of the photocell type presents serious problems in conducting the photocell output signals from the rotating photocell (in the detecting head) to the stationary circuit portions of stop motion systems. Simple wire leads or conductor cables leading from the rotating subassembly components to the stationary subassembly components of the system are obviously unusable due to the relative motion present. Simple collector ring or slip ring coupling is not a satisfactory solution, as it introduces intolerable noise problems.

An object of the present invention, therefore, is the provision of a novel fabric flaw detector system for circular knitting machines wherein the fabric tube produced by the knitting machine is not rotated during knitting.

Another object of the present invention is the provision of a novel photocell type fabric flaw dettector system for revolving creel type circular knitting machines, wherein a novel subdivision of rotating and stationary components of the detector system with a particular collector ring arrangement are provided to secure reliable performance with such knitting machines.

Another object of the present invention is the provision of a novel detector system of the type described in theimmediately preceding paragraph, wherein an amplifier and power supply are both located inside the fabric tube to rotate with the detector head, and the remaining system components are fixed on a stationary part of the knitting machine, only a single wire lead from a step down transformer and control relay in the stationary system subassembly being connected through a collector ring to the power supply in the revolving subassembly to simplify the system and minimize collector ring noise effects.

Another object of the present invention is the provision of such a flaw detector system for revol'ving creel circular knitting machines, wherein a circular band or ring of retro-reflective material extends around the fabric tube in alignment with the optical axis of the detector head to increase light variations when a hole or similar fabric defect is encountered and provide a high output signal from the detector photocell.

Other objects, advantages, and capabilities of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawing illustrating preferred embodiments of the invention.

In the drawings:

FIGURE 1 is a diagrammatic view of the fabric flaw detector system of the present invention;

FIGURE 2 is a fragmentary elevation of the rotary subassembly of the fabric flaw detector system shown in association with adjacent components of a revolving creel circular knitting machine, with parts broken away;

FIGURE 3 is a horizontal section view of the rotary subassembly of the fabric flaw detector system, taken along the line 33 of FIGURE 2;

FIGURE 4 is a schematic diagram of the transformer, rectifier and control relay circuit provided in the stationary subassembly of the fabric flaw detector system; and

FIGURES 5 and 6 are schematic diagrams of the amplifier circuit and regulated power supply circuit, respectively, incorporated in the rotary subassembly of the fabric flaw detector system.

Referring to the drawings, wherein like reference character designations correspond to parts throughout the several figures, and particularly to FIGURES 1, 2 and 3, the fabric flaw detecting system of the present invention comprises a stationary subassembly, generally indicated by the reference character 10 in FIGURE 1 and sometimes referred to as the control box, which is adapted to be mounted on a suitable stationary support, for example, on a stationary portion of the circular knitting machine frame (not shown). This stationary subassembly or control box 10 houses as the principal components thereof a transformer T-l, control relay 11, a manual reset switch S-1 and an alarm indicator lamp L1, which will be later referred to in greater detail.

Since on rotary creel type knitting machines, the creel and head structure located above the needle cylinder and sinkers rotates about a vertical axis while the lower machine frame, needle cylinder, sinkers and associated parts do not rotate and thus the fabric tube knitted by the needles does not rotate but rather is translated axially downwardly from the circular needles without rotation,

the flaw sensing components of the fabric flaw detecting system must therefore rotate so as to scan around the fabric tube as the latter moves downwardly from the needles to detect holes or similar flaws which might occur at any portion of the fabric tube. In order to accomplish this, the system of the present invention employs a revolving subassembly 12 which consists basically of a detector head 13, a transistorized amplifier 14, and a regulated power supply 15 all mounted on a suitable support so as to rotate within the fabric tube immediately below the zone of the circular set of latch needles. These revolving subassembly components are so arranged and connected that only a single wire connection is required between the revolving subassembly 12 and the stationary control box 10, this being a wire lead 16, 16' communicating current between the coil of the control relay 11 and the regulated power supply 15, which is interrupted by a wiper contact 17 and collector ring 18 permitting continuous electrical communication through the connecting lead 16, 1-6 at all times notwithstanding rotation of the revolving subassembly 12. This system is diagrammatically illustrated in FIGURE 1 and the physical arrangement and location of the revolving subassembly and its relationship to adjacent components of the revolving creel circular knitting machine are shown in FIGURES 2 and 3.

As will be observed from FIGURES 2 and 3 the revolving subassembly components are all supported in depending relation from an annular mounting plate 20 having a central opening to receive the usual enlarged boss or collar 21 on the vertical shaft 22 forming part of the upper head structure, generally indicated by the reference character 23, of the conventional rotary creel circular knitting machine, the cam ring and dial cap portions 23a of the knitting machine being shown somewhat schematically in FIGURE 2. The mounting plate 20 has a depending clamping collar structure 24 depending therefrom in surrounding relation to the boss or collar 21 and provided, for example, with headed set screws threaded in the lower annular collar portion to abut and fix the mounting plate 20 on the boss or collar 21 of the shaft 22 for rotation with the latter.

The detector head 13 is of the type disclosed in said co-pending application, Ser. No. 417,697, and comprises a drilled mounting block 25 supporting a suitable lamp 26 and photocell 27 arranged at right angles to each other together with a semi-transparent mirror 28 and a lens 29, which may be either a spherical lens or a cylindrical lens. These components are arranged in the mounting block so that light from the lamp 26 is projected through the mirror 28 and lens 29 toward the fabric tube, indicated by the reference character 30, as the fabric passes downwardly from the zone of the needles and sinkers, and light returning from the direction of the fabric is directed by the lens 29 to the semi-transparent mirror 28 and reflected to the photocell 27. The detector head 13 is suitably supported in depending relation from the mounting plate 20' by means such as the mounting post 3-1.

The housing 3-2 is also supported in depending relation from the mounting plate 20 in spaced angular relation to the detector head 13 and houses the amplifier 14 and regulated power supply 15. With this arrangement, the electrical connections between the detector head 13, on the one hand, and the regulated power supply 15 and amplifier 14 in the housing 32, on the other hand, can be made by simple electrical leads extending between these components. The connections between the amplifier 14 and regulated power supply 15 are made internally of the housing 32 and a simple three-conductor shielded cable may be connected from the amplifier 14 through the center of the hollow vertical shaft 22 to a manual gain-control unit 33 fixed on one of the support rods or posts 34 of the revolving head 23 so that the gain-control 33 rotates with the revolving head 23 and revolving subassembly 12. Only a single wire lead, therefore, extending from the input terminal of the transformer T-2 (to be later described) of the regulated power supply 15 needs to be connected to the stationary control box 10 with respect to which the revolving subassembly moves, this being effected by a single lead, indicated at 16' in FIGURE 1, connected to the collector ring 18 fixed on the support posts 34 of the revolving head by suitable insulated mounts, which is continuously engaged by the wiper contact 17 during rotation of the revolving head 23 to continuously electrically interconnect the stationary control box 10 and the revolving subassembly 12.

As is illustrated in FIGURE 2 and schematically indicated in FIGURE 1, a thin, axially elongated tape ring 35 surrounds and is disposed outwardly of the fabric tube 30 in the optical path of the detector head 13 so that the fabric passes between the tape ring 35 and the detector head 16, the tape ring 35 being supported for example by a suitable mounting bracket 36 fixed to the stationary ring 37 of the usual revolving creel type circular knitting machine. The inner surface of the tape ring 35 is covered with retro-reflective material, for example retro-reflective tape, of the type marketed under the name SCOTCHLITE, by Minnesota Mining and Manufacturing Company, having the property of returning light along the same path as the incident light rays regardless of the angle of incidence. By this arrangement, light from the lamp 26 of the detector head 13 passing through the semitransparent mirror 28 and lens 29 strikes the fabric tube 30, and if a hole or similar flaw is encountered in the fabric, high intensity light is transmitted through the hole on to the retro-reflective tape 35 and is redirected back along the incident ray path through the lens 29 and is redirected by the mirror 28 on to the photo sensitive surface of the photocell 27 reducing the resistance of the photocell. Since the path of retro-reflective light is similar to the path of incident light, the retro-reflective tape returns a maximum reflected signal toward the point of origin with a minimum of incident energy.

It will be noted from FIGURE 2 that a circular spreader 38 is also located within the fabric tube 30 below the scanning station and may be supported for example from the vertical shaft or spindle 22 so as to maintain the fabric tube in a desired spread configuration at the scanning station.

Referring now to the details of the electrical circuits included in the control box 10 and in the amplifier 14 and regulated power supply 15 illustrated in FIGURES 4, 5 and 6 and particularly to the circuit of the control box 10 illustrated in FIGURE 4, the primary of the transformer T-1, which is a step-down transformer designed to produce 18 volts AC across its secondary, is supplied with nominal 118 volts AC from a conventional supply through a master switch S-2 and a fuse in one of the input leads to the transformer primary, a suitable indicator lamp L-2 being provided across the transformer primary if desired. One end of the secondary of transformer T-1 is grounded and the other end is connected through the manual reset switch 5-1 to a variable resistor, for example, a 5 ohm resistor R-l, the movable contact or wiper of which is connected by lead 40 to a rectifier networ-k generally indicated at 41 formed of diodes D1, D-2, D3, and D4 suitably connected across the coil of control relay 11 to apply a D-C voltage across the coil of the control relay 11. A lead 42 is also connected from the ungrounded end of the secondary of T-l to the movable contact of contact set 11a of control relay 11, the normally open (when relay 11 is de-energized) stationary contact of which is connected by lead 43 to the upper end of variable resistor R1. Leads 44 connect the alarm lamp L-1, which like indicator lamp L2 may be a NE 51 neon glow lamp, through the normally closed stationary contact and movable contact arm of relay contact set 11b across the primary of transformer T-l, causing the alarm lamp L-1 to be energized only when the master switch 5-2 is closed to supply power to the primary of transformer T-1 and control relay 11 is de-energized. Contact set 11c of control relay 11 is connected as indicated in FIGURE 4 to the conventional stop motion system of the knitting machine which is normally actuated by yarn breakage and the like. The contact set 110 completes a circuit from the hot lead of the conventional stop motion system to the machine frame to stop the knitting machine when a fabric flaw is detected signified by de-energizing of the control relay 11.

The lower end of variable resistor R-l is connected to the bottom of the rectifier network 41 and through lead 16 to the wiper or contact 17 engaging the collector ring 18.

The collector ring 18 in'turn is connected by lead 16' to the primary winding of the transformer T-Z in the regulated power supply schematically illustrated in FIG- URE 6, the opposite end of the primary of T-2 being grounded to the machine frame.

The control relay 11 is a 6-volt DC type relay designed to fall out or be de-energized when less than 6 volts DC is-applied across its coils. The circuit disclosed in FIG- URE 4 permits some time delay on fall out to prevent false stops caused by contactor bounce, this being accomplished by rectifying the AC voltage across variable resistor R1 and by the 1000 mfd. capacitor C-1 across the coil of control relay 11. The variable resistor R-1 is adjusted to permit proper voltage to be applied to the coil of control relay 11 for proper pull in and fall out action. Since some current always flows through the primary of transformer T-2 when contacts 11a are closed, this may be sufficient to keep control relay 11 energized if resistor R-1 is not properly adjusted to cause deenergization of relay 11 upon detection of a fabric defect as hereinafter described.

Referring now to FIGURE 6, illustrating the schematic diagram of the regulated power supply 15 the transformer T2 has three secondary coils, designated by reference characters T-Za, T-2b and T-Zc. Secondary winding T-Za applies 150 volts AC across the rectifier diode network 45, whose output leads are connected through a filter circuit comprising two 40 mfd. capacitors C-2 and C-3 and and a 39K ohm resistor R-2, and across a 150K ohm resistor R-3. The voltage across the resistor R-3 is applied to the pair of series connected zener diodes D5 and D-6 to provide regulated 150 volts DC to the photocell 27 in the detector head 13 connected to terminal 46.

The second transformer secondary winding T-Zb applies 28 volts AC to the diode rectifier network 47, the output from which is filtered by the filter network formed of mfd. capacitors C4 and C-5, the latter having a 47K ohm resistor R-4 across the same, and including 470 ohm resistor R-5, the filtered output being applied across zener diode D7 to produce a regulated 27 volt DC supply for the amplifier 14 at terminal 48.

The 27 volt regulated DC output at the top of zener diode D7 is also applied across a voltage divider consisting of a 20K ohm resistor R-G, a 5K ohm potentiometer R7 and a 3K ohm resistor R-S connected in series to ground. The movable contact or slider or potentiometer R-7 is connected to the base of transistor Q-l to bias the same, the emitter of which is connected in common with the emitter of transistor Q-Z through a 2.2K resistor R9 to ground. The collectors of the two transistors Q-l and Q2 are connected through 4.7K ohm resistors R-10 and R-11 and a common 6.8K ohm resistor R-12 to the 27 volt regulated DC supply, and the junction between resistor R-12 and the two collector resistors R-lil and R-11 being connected to terminal 49 for connection to the anode of the silicon controlled switch SCS (or, if desired, a silicon controller rectifier on SCR) in the amplifier 14, to be later described. The collector of the transistor Q2 below the resistor R-11 is connected to the base of transistor Q3, the emitter of which is connected in turn through diode D8 to the base of transistor Q-4 in a Darlington type configuration. The emitter of transistor Q-4 is connected through 10K resistor R-13 to ground, the junction between the resistor R-13 and the emitter of transistor Q4 being connected by lead 50 to the base of transistor Q2. The collectors of the two transistors Q-3 and Q-4 are supplied with about 12 volts DC obtained by applying 12.6 volts AC derived from the secondarying winding T-Zc of transformer T-2 to the diode rectifier network 51, whose output is filtered by a 2.5 ohm resistor R44 and a 500 mfd. capacitor C6 across which is connected a 10K ohm resistor R-15. The rectified and filtered voltage of about 12 volts DC thus produced is applied by lead 52 to the collectors of transistors Q-3 and Q-4. The transistors Q-l and Q-2 form a differential amplifier arrangement and the bias on the base of transistor Q-l is adjusted by potentiometer R-7 to produce biasing of transistors Q-2, Q-3 and Q-4, such that appropriate current flows to produce 5 volts DC across the lamp 26 of the detector head 13 which is applied through terminals 53 to the lamp 26. Resistor R-13 provides a return path for transistor Q-4 in the event the detector head is disconnected or lamp 26 burns out.

Referring now to FIGURE 5 illustrating the circuit of the amplifier 14, there is illustrated an amplifier circuit generally designated by reference character 55 having lower gain characteristics which is adequate for most fabrics, which is provided with a low gain-high gain selector switch S-3 and a high gain circuit 56 which may be interconnected with the lower gain amplifier circuit 55 when required. However, it will be understood that the amplifier 14 may consist only of the lower gain amplifier circuit 55. The amplifier circuit 55 comprises an emitter follower stage 57 for impedance matching, comprising a transistor Q-5 whose base is connected through a .1 mfd. capacitor C-7 to the top of a K resistor R-16 and to the photocell 27 in the detector head 13. A voltage divider consisting of the 4.7 mdg.

resistor R-17 and the 470K resistor R48, the latter having a .005 mfd. capacitor across the same, supplies forward bias for the transistor Q5. A diode D-9 is also connected to the base of the transistor Q to prevent negative pulses on the base from damaging the transistor. A 10K potentiometer R-19 is connected between the emitter of transistor Q-S and ground and the movable contact or slider of potentiometer R-19 is connected to one of the center terminals of the switch 8-3. In the low gain position of selector switch 8-3, the signal from the slider of potentiometer R-19 is coupled through a .47 mfd. capacitor C8 to the collector of transistor Q-6 forming a time delay stage 58, the base of which is connected to a resistor-capacitor network formed of 47 mfd. capacitor (3-9, 100K resistor R-2tl and 47K resistor R-Zl connected between +27 volt DC and ground. The purpose of the time delay stage 58 is to permit the machine to knit by a flaw on start up.

The collector of the transistor Q6 is connected through a 10K resistor R-22 to ground and through a 1K resistor R23 to the gate of the silicon controlled switch SCS, a diode D-ltl and a .01 mfd. capacitor C-10 being connected between the gate and ground. The cathode of the silicon controlled switch SCS is connected to the junction of a 2.7K resistor R-24 and a 100 ohm resistor R-25 forming a voltage divider between +27 volts DC and ground, and the anode of the SCS is connected through lead 59 to the terminal 49 of the regu-. lated power supply at the junction between resistor R12 and the two resistors R1(), and R-ll.

In the event higher gain is needed, adjustment of the selector switch S-3 to the high gain position connects the slider of potentiometer R-19 through lead 60 to the input of the high gain circuit 56, formed for example of a plurality of stages having transistors Q-7, Q-8, Q9., Q-10 and Q-11 therein connected as illustrated in FIG- URE 5.

In the operation of the electrical circuits described, assuming the selector switch S-3 to be in the low-gain position, operation of the scanner is initiated by closing the master switch S-2 and the manual reset switch S1. This applies voltage to the coil of the control relay 11, shifting its contacts to the opposite position from that shown in FIGURE 4, establishing the holding circuit through contacts 11a and lead 43 and applying voltage through leads 16, 16', wiper 17 and collector ring 18 to the transformer T4 of the regulated power supply 15. When current flows through the transformer T-2, 27 volts DC. is applied to the amplifier circuit of FIGURE 5, charging the 47 mfd. capacitor C-9 through resistors R- and R-21. As long as sufficient current is flowing through resistors R2() and R-21, a forward bias is applied to the 'base of transistor Q6 which turns it on and acts as a short circuit across resistor R22. This prevents any signal from the emitter follower stage 57 of the amplifier from reaching the gate of the silicon controlled switch SCS and causing it to fire. As soon as the timing capacitor C-9 becomes sufliciently charged, which takes about 15 seconds, current decreases through the resistor R-20 and R-21, and transistor Q6 stops conducting and no longer blocks incoming signals to the gate of the silicon controlled switch SCS. This introduces a time delay in the response of the SCS to holes or flaws signals on start up so that the machine will not be immediately stopped again on attempted start up when a hole or fabric flaw is still in the field of view of the detector head 13.

A hole or similar flaw in the fabric tube passing between the detector head 13 and the retro-reflective material on the tape ring 35 causes more light to strike the photocell 27 as compared to the light intensity striking the photocell for normal fabric, which causes the resistance of the photocell to decrease. This causes more current to flow through the resistor R-16, thus generating a positive pulse which is applied to the base of transistor Q-S by the capacitor C-7. The transistor Q-S being conneoted in an emitter follower configuration, a positive pulse appears across the potentiometer R-19, which is the circuit element in the gain control unit 33, this control being set as high as possible without having false stops. The voltage on the slider of gain control potentiometer R-19 is applied to the collector of time delay transistor Q-6, and assuming the time delay transistor Q6 is non-conducting (which is its normal state after the time delay period following start up), this voltage will be applied through resistor R-23 to the gate of the silicon controlled switch SCS and cause it to fire. Firing of the silicon controlled switch SCS as the result of the hole or flaw, provides a low resistance path to ground, thus removing most of the supply voltage for the transistors Q-1 and Q-2. This removes the forward bias from transistors Q-3 and Q-4, causing the lamp current to the lamp 26 of the detector head 13 to drop drastically. When the lamp load has been thus removed from the regulated power supply, insufiicient current is drawn by the regulated power supply 15 to maintain a 6 volt drop across the coil of the control relay 1 1, so that the relay 11 then drops out, establishing the supply circuit for the alarm indicator lamp L-1 through contacts 11b and establishing the supply circuit through contacts 11c to the stop motion system on the machine to stop the machine.

Upon closing the manual reset switch 5-1, the coil of control relay 11 is again energized to shift the relay contacts and re-establish operation in the manner previously described. The silicon diode D8 provided between the transistor Q-3 and Q4 is for the purpose of lowering the lamp regulator output when the silicon controlled switch SCS is fired. Without this diode D8, the small voltage drop across the SCS would cause some current to flow through the lamp. The presence of this diode D-8 greatly lowers this current and makes the fall out of control relay 11 more positive.

The silicon controlled switch and transistors of the previously described circuits may, for example, be the following commercially available types:

Q4, 4. T1848 Q-3 2N3053 Q-4 2N3054 Q5, Q-9 TNSS Q6, Q-7, Q-8, Q-10, Q-11 TN53 scs 3N58 While the detector head 13 is illustrated in FIGURE 3 in a position inclining the optical axis of the lens 29 relative to the radius of the center axis of shaft 22 through the point on the fabric 30 intercepting the optical axis (or the tangent through said point) the optical axis of the detector head may be disposed at various positions from a precisely radially outwardly projecting position to an inclined position forming an acute angle relative to the radius of the shaft axis. The latter has been found to be highly effective with very thin fabrics, while the radial position provides good results with thicker fabrics.

While only one form of the present invention has been particularly shown and described, it will be apparent that various modifications may be made Within the spirit and scope of the invention, and it is desired, therefore, that only such limitations be placed on the invention, as are imposed by the prior art and set forth in the appended claims.

What is claimed is:

1. Fabric flaw detecting apparatus for inspecting a tubular knit fabric produced at a needle station of a circular knitting machine of the rotary creel type as the fabric moves downwardly from the needle station without rotation substantially centered about a vertical reference axis to detect runs, holes, and similar aperture flaws in the fabric tube, comprising a first subassembly including a detector head and associated circuit means positioned in fixed relation to each other and disposed below said needle station within said fabric tube, said detector head including light source means for directing light rays along a selected light ray axis in a confined beam toward fabric tube portions lying outwardly of said first subassembly and a photocell to receive light returned from the fabric portion intercepting said beam, said associated circuit means including means for amplifying output signals produced by said photocell, means supporting said detector head and circuit means of said subassembly for rotation as a unit about said reference axis at an angular velocity relative to the rate of movement of said fabric tube downwardly from said needle station to cause said beam to scan circumferentially around the fabric tube and intercept all portions of the fabric tube, a surface of reflective material disposed outwardly of the fabric tube in the path of said beam to return toward the detector head light passing through aperture flaws in the fabric, and a second subassembly supported at a stationary position with respect to which the first subassembly rotates electrically coupled with said first subassembly including circuit means intercoupled with said associated circuit means of said first subassembly for producing a signal indicative of flaw detection responsive to a selected level of light activation of said photocell.

2. Fabric flaw detecting apparatus as defined in claim 1, wherein said surface of reflective material comprises the inwardly facing surface of a stationary ring supported in outwardly encircling relation to the fabric tube substantially concentric with said reference axis and aligned I radially thereof with said detector head.

3. Fabric flaw detecting apparatus as defined in claim 2, wherein the sole electrical coupling between said first and second subassemblies is formed of ground return means electrically communicating each of said subassemblies with the knitting machine frame and a single wire conductor interconnecting variable currents between said circuit means of said second subassembly and said associated circuit means of said first subassembly including a collector ring supported for rotation with said first subassembly and the rotary creel of the knitting machine and a stationary wiper contact in continuous electrically conductive engagement with the collector ring during rotation thereof.

4. Fabric flaw detecting apparatus as defined in claim 3, wherein said associated circuit means of said first subassembly comprises an amplifier coupled to said photocell, a regulated power supply supplying regulated voltage to said photocell and said light source means, and means intercoupled with said amplifier and regulated power supply responsive to amplifier signals denoting a selected level of light activation of said photocell upon interception of said beam by an aperture flaw to reduce current drawn by said power supply, and said current means of said second subassembly includes means responsive to a selected reduction of current drawn by said regulated power supply reflected through said single wire conductor to produce an alarm signal denoting flaw detection.

5. Fabric flaw detecting apparatus as defined in claim 4, wherein said last-mentioned means of said second subassembly comprises a current sensitive relay having a coil 7 through which current is drawn in preselected relation to the current drawn by said regulated power supply, and said means intercoupled with said amplifier and regulated power supply comprises a normally non-conducting silicon controlled switch responsive to said amplifier signals to conduct and thereby reduce the current drawn by said regulated power supply to a level causing deenergizing of said relay.

6. Fabric flaw detecting apparatus as defined in claim 1, wherein the sole electrical coupling between said first and second subassemblies is formed of ground return means electrically communicating each of said subassemblies with the knitting machine frame and a single Wire conductorinterconnecting variable currents between said circuit means of said second subassembly and said associated circuit means of said first subassembly through a collector ring supported for rotation with said first subassembly and the rotary creel of the knitting machine and a stationary wiper contact in continuous electrically conductive engagement with the collector ring during rotation thereof.

7. Fabric flaw detecting apparatus as defined in claim 1, wherein said-associated circuit means of said first subassembly comprises an amplifier coupled to said photocell, a regulated power supply supplying regulated voltage to said photocell and said light source means, and means intercoupled with said amplifier and regulated power supply responsive to amplifier signals denoting a selected level of light activation of said photocell upon interceptionof said beam by an aperture flaw to reduce current drawn by said power supply, and said circuit means of said second subassembly includes means responsive to a selected reduction of current drawn by said regulated power supply to produce an alarm signal denoting flaw detection.

8. Fabric flaw detecting apparatus as defined in claim 7, wherein said last-mentioned means of said second sub assembly comprises a current-sensitive relay having a coil through which current is drawn in preselected relation to the current drawn by said regulated power supply, and said means intercoupled with said amplifier and regulated power supply comprises a normally non-conducting silicon controlled switch responsive to said amplifier signals to conduct and thereby reduce the current drawn by said regulated power supply to a level causing de-energizing of said relay.

9. Fabric flaw detecting apparatus as defined in claim 8, wherein the sole electrical coupling between said first and second subassemblies is formed of ground return means electrically communicating each of said subassemblies with the knitting machine frame and a single wire conductor interconnecting variable currents between said relay and said regulated power supply through which power is supplied to said power supply, said conductor including collector ring means intermediate the ends thereof comprising a collector ring supported for rotation with said first subassembly and the rotary creel of said knitting machine and connected directly to a first portion of said conductor connected to said power supply and a stationary wiper contact in continuous electrically conductive engagement with the collector ring during rotation thereof and connected directly to a second portion of said conductor connected to said relay.

10. Fabric flaw detecting apparatus as defined in claim 1, wherein said light source means includes a lamp arranged substantially at right angles to said photocell and a lens disposed to direct light rays from said lamp along said ray axis toward said fabric tube portions, said detector head including a semi-transparent mirror disposed between said lamp and lens at an angle to reflect light returned from the fabric through said lens toward said photocell, said lens producing a light pattern at the fabric which is narrow circumferentially of the fabric and spans a suflicient length axially of the fabric tube to be intercepted by all portions of the fabric during scanning thereof.

11. Fabric flaw detecting apparatus as defined in claim 2, wherein said reflective surface of said ring is retroreflective material which returns light along the incident light ray path thereof, and said detector head being disposed to direct light toward said fabric tube along a ray axis inclined at a selected acute angle to the radius of said reference axis passing through the intercept of said ray axis with the fabric tube.

12. Fabric flaw detecting apparatus as defined in claim 7, wherein said last-mentioned means of said second subassembly comprises a current sensitive relay having a coil through which current is drawn in preselected relation to the current drawn by said regulated power supply to de- 1 1 1 2 energize the relay by reduction of current drawn by the 2,669,107 2/1954 Phillips et al. 66166 regulated power supply responsive to said amplifier sig- 2,694,305 11/ 1954 Lafevillade 66166 XR nals upon detection of a fabric flaw by the photocell, said 2,878,589 3/1959 Mongello, associated circuit means of said first subassembly includ- 3,065,615 11/1962 Abrams 66*166 ing time delay means for preventing production of ampli- 5 3,116,621 1/1964 Klein et a1.

fier signals denoting detection of a fabric flaw for a selected time delay period following each start up of the 3276227 10/1966 Althaus et 66 166 fabric flaw detecting apparatus. FOREIGN PATENTS References Cited 1,167,238 7/ 1958 France.

UNITED STATES PATENTS 2 611 097 9/1952 Stanley et a1 WM. CARTER REYNOLDS, Primary Examiner. 

1. FABRIC FLAW DETECTING APPARATUS FOR INSPECTING A TUBULAR KNIT FABRIC PRODUCED AT A NEEDLE STATION OF A CIRCULAR KNITTING MACHINE OF THE ROTARY CREEL TYPE AS THE FABRIC MOVES DOWNWARDLY FROM THE NEEDLE STATION WITHOUT ROTATION SUBSTANTIALLY CENTERED ABOUT A VERTICAL REFERENCE AXIS TO DETECT RUNS, HOLES, AND SIMILAR APERTURE FLAWS IN THE FABRIC TUBE, COMPRISING A FIRST SUBASSEMBLY INCLUDING A DETECTOR HEAD AND ASSOCIATED CIRCUIT MEANS POSITIONED IN FIXED RELATION TO EACH OTHER AND DISPOSED BELOW SAID NEEDLE STATION WITHIN SAID FABRIC TUBE, SAID DETECTOR HEAD INCLUDING LIGHT SOURCE MEANS FOR DIRECTING LIGHT RAYS ALONG A SELECTED LIGHT RAY AXIS IN A CONFINED BEAM TOWARD FABRIC TUBE PORTIONS LYING OUTWARDLY OF SAID FIRST SUBASSEMBLY AND A PHOTOCELL TO RECEIVE LIGHT RETURNED FROM THE FABRIC PORTION INTERCEPTING SAID BEAM, SAID ASSOCIATED CIRCUIT MEANS INCLUDING MEANS FOR AMPLIFYING OUTPUT SIGNALS PRODUCED BY SAID PHOTOCELL, MEANS SUPPORTING SAID DETECTOR HEAD AND CIRCUIT MEANS OF SAID SUBASSEMBLY FOR ROTATION AS A UNIT ABOUT SAID REFERENCE AXIS AT AN ANGULAR VELOCITY RELATIVE TO THE RATE OF MOVEMENT OF SAID FABRIC TUBE DOWNWARDLY FROM SAID NEEDLE STATION TO CAUSE SAID BEAM TO SCAN CIRCUMFERENTIALLY AROUND THE FABRIC TUBE AND INTERCEPT ALL PORTIONS OF THE FABRIC TUBE, A SURFACE OF REFLECTIVE MATERIAL DISPOSED OUTWARDLY OF THE FABRIC TUBE IN THE PATH OF SAID BEAM TO RETURN TOWARD THE DETECTOR HEAD LIGHT PASSING THROUGH APERTURE FLAWS IN THE FABRIC, AND A SECOND SUBASSEMBLY SUPPORTED AT A STATIONARY POSITION WITH RESPECT TO WHICH THE FIRST SUBASSEMBLY ROTATES ELECTRICALLY COUPLED WITH SAID FIRST SUBASSEMBLY INCLUDING CIRCUIT MEANS INTERCOUPLED WITH SAID ASSOCIATED CIRCUIT MEANS OF SAID FIRST SUBASSEMBLY FOR PRODUCING A SIGNAL INDICATIVE OF FLAW DETECTION RESPONSIVE TO A SELECTED LEVEL OF LIGHT ACTIVATION OF SAID PHOTOCELL. 